This book is focused on the Holy Spirit, but not in isolation from the Father and the Son. There is a unity of purpose in the three 'manifestations' of God that demonstrate that One God is presented to us in three 'roles'. - The Father sends the Spirit;- The Spirit comes to the disciples; and- The Spirit bears witness to Jesus the Messiah. This unity of purpose involves each of the 'Three' playing their 'role' in calling the sinner to embrace "the salvation that is in Christ Jesus". The Trinity, and specifically the Holy Spirit, is related to 'man's' place in that purpose. Initially the author examines the role of the Spirit in regard to all mankind, believers or otherwise, for His ministry involves not just Christians but mankind in general. He also goes on to show that what has been revealed of the Holy Spirit in the Bible developed as we move through the pages on Scripture. We find His ministry changes according to God's plan and purpose.